A pit type unwheeling machine is used in non-uncoupling overhaul operation of the entire train of a China Railway High-speed (CRH) train , high-speed train, high-power locomotive or urban rail vehicle. By means of the pit type unwheeling machine, a vehicle bogie can be replaced and electrical devices at the lower part of the bodywork or on the roof can be overhauled and replaced.
When a CRH train is lifted, first, the entire train (with 16 cars or 8 cars per set) is synchronously lifted to a certain height by using a bogie lifting unit and the bogie is disassembled, then, the cars of the train are supported by the bodywork lifting unit.
The load-carrying head portion of the bodywork lifting unit is required to have a transverse adjustment function when unloaded because different CRH train cars have different lifting points. Meanwhile, a train with 16 cars per set contains 32 bogies while the length of train formation is more than 400 meters and the weight is up to 960 tons. After the overhaul operation of the entire train is completed, there is great difficulty in installing bogies, and therefore, a local transverse fine adjustment between the bodywork and the bogie is required, that is to say, in the situation that the bodywork lifting unit is loaded (also known as “load-carrying”), the load-carrying head of the bodywork lifting unit can make a certain amount of transverse fine adjustment together with the bodywork.
The traditional load-carrying head of a bodywork lifting unit mainly includes the two following types:
(1) None of the load-carrying heads of the pair of left and right bodywork lifting units can be adjusted, which can only be used for one single type of train, and the train formation is limited to 4 to 6 cars and usually used in a common subway train;
(2) Both the load-carrying heads of the pair of left and right bodywork lifting units can be transversely adjusted when loaded, but the adjustable portion is of a fully rigid structure. A big force is needed during the fine adjustment of the load-carrying head, and the left and right sides of the car needs to be synchronously adjusted at the same time, a person in one side pushes it in and a person in other side pulls it out together to realize the adjustment, due to the rigid structure, the fine adjustment of the load-carrying head with load is completely dependent on the overcome of the mechanical deformation of the device structure itself, therefore, a very big force and a handle mechanism are needed and it is very inconvenient for use.